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89 results on '"Kogaki, Tetsuya"'

4. Les of Flow Around a Square Cylinder

Author

Kogaki, Tetsuya, Kobayashi, Toshio, Taniguchi, Nobuyuki, Hutchinson, P., editor, Rodi, W., editor, Chollet, Jean-Pierre, editor, Voke, Peter R., editor, and Kleiser, Leonhard, editor

Published
1997
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9. Dynamic Analysis of the Two-Bladed Horizontal Axis Wind Turbine

Author

Aoki, Shigemitsu, Kogaki, Tetsuya, and Sakurai, Kenichi

Subjects
Eulerian coordinate system, Hard-wear in the Loop System, Real-time Simulation
Abstract

First International Symposium on Flutter and its Application (May 15-17, 2016. Mielparque-tokyo), Minato-ku, Tokyo, Japan, In order to make an approach according to the dynamic characteristics of the two-bladed Horizontal axis wind turbine, that is substantially unstable and non-linear motion, the basic equations were derived by Lagrange's method on Eulerian coordinate system. An aero-elastic simulation model named AIST-RAM (AIST Real-Time Model), that represents characteristics of the motion was developed referring to the basic equations and another factors such as an aerodynamic force acting on the blades that is strongly affected by the motion and elasticity of the blades itself. Also, a scale model of the multi-megawatt horizontal-axis wind turbine was constructed as well as the specified management system called Hard-wear in the Loop (HIL). Through the successive evaluation by wind-tunnel testing and field testing accompanied with real-time simulation arranged by the Hard-wear in the Loop System, the credibility of the simulation soft-wear is gradually confirmed along with the clear understanding as to a characteristics of the teetered-hub system that has ever been discussed among the industry., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630046077, レポート番号: JAXA-SP-16-008E

Published
2017

10. Research and Development of Next-Generation Wind Turbine Generation Technology using Wind Tunnel Experiments and Other Techniques

Author

Abe, Hiroyuki and Kogaki, Tetsuya

Abstract

第3回風洞技術の開発と応用シンポジウム: 風洞シンポジウム2014 (2014年10月24日. 日産自動車株式会社テクニカルセンター), 厚木市, 神奈川県, Symposium on Developments and Applications of Wind Tunnel Technologies 3rd meeting (October 24, 2014. Advanced Technology Center, NISSAN MOTOR CO., LTD.), Atsugi, Kanagawa, Japan, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1530054014, レポート番号: JAXA-SP-15-021

Published
2016

22. 風洞実験等を活用した次世代風力発電技術の研究開発

Author

阿部, 裕幸, 小垣, 哲也, Abe, Hiroyuki, Kogaki, Tetsuya, 阿部, 裕幸, 小垣, 哲也, Abe, Hiroyuki, and Kogaki, Tetsuya

Abstract

会議情報: 第3回風洞技術の開発と応用シンポジウム: 風洞シンポジウム2014 (2014年10月24日. 日産自動車株式会社テクニカルセンター), 厚木市, 神奈川県, 形態: カラー図版あり, Meeting Information: Symposium on Developments and Applications of Wind Tunnel Technologies 3rd meeting (October 24, 2014. Advanced Technology Center, NISSAN MOTOR CO., LTD.), Atsugi, Kanagawa, Japan, Physical characteristics: Original contains color illustrations

Published
2016

24. Assessment of the offshore wind resource in Japan with the ASCAT microwave scatterometer.

Author

Takeyama, Yuko, Ohsawa, Teruo, Shimada, Susumu, Kozai, Katsutoshi, Kawaguchi, Koji, and Kogaki, Tetsuya

Subjects
SCATTERING (Physics), WIND speed measurement, RADAR, WEATHER forecasting, METEOROLOGICAL research
Abstract

We analysed wind speed and direction off the coast of Japan using data from the satellite-borne Advanced Scatterometer (ASCAT) and the Weather Research and Forecasting model (WRF), validated these data using in situ wind measurements from 20 buoys, and evaluated the effect of the long time intervals from ASCAT observations on wind resource assessment. More than 25 km from the coast, and at heights of 10 m, the ASCAT wind speed has negative biases of up to 3.4% and root mean square errors of up to 18.5%; its wind direction has 11° to 27° of mean absolute error compared to buoy measurements at a height of 10 m. These accuracies are better than either the expected accuracies reported in the technical manual or those simulated with WRF with its spatial resolution of 10 km. We also evaluated long-term average ASCAT wind speeds in comparison to 4- and 5-year averages of in situ buoy wind speeds measured at three buoys, with resulting differences of -0.3%, -6.3%, and - 1.6%. Furthermore, wind roses show that appearance frequencies of the ASCAT wind direction for the long term are in a good agreement with those of the measurements at the three buoys. Our results show that the ASCAT-derived wind speed and direction are appropriate more than 25 km from the coast, and that the long time interval between ASCAT observations has an insignificant effect on wind resource assessment, if at least 4 or 5 years of averaged ASCAT data are used. [ABSTRACT FROM AUTHOR]

Published
2019
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26. 乱流LESに適した一般座標系差分スキームについて

Author

Kogaki, Tetsuya, Taniguchi, Nobuyuki, Matsuo, Yuichi, 小垣 哲也, 谷口 伸行, 松尾 裕一, Kogaki, Tetsuya, Taniguchi, Nobuyuki, Matsuo, Yuichi, 小垣 哲也, 谷口 伸行, and 松尾 裕一

Abstract

In order to conduct Direct Numerical Simulations (DNS) or Large Eddy Simulations (LES) of turbulent flow in complicated flow geometry, accurate finite difference methods are needed in generalized curvilinear coordinate system. Recently, it was shown that the analytical conservative properties of the set of basic equations are needed to be satisfied properly even in discrete basic equations in order to obtain accurate and stable solutions in simulations of incompressible turbulent flow using finite difference method. In this paper, it is demonstrated that the analytical conservative properties of the coordinate transformed basic equations for incompressible viscous flows are identical with that in Cartesian coordinates. The basic equation treated here are the continuity equation, the Navier-Stokes equation and the transport equations of the square value of velocity components and the kinetic energy. The finite difference schemes in generalized curvilinear coordinate system that are suitable for simulation of incompressible turbulent flow are constructed from relatively simple extension of the proper finite difference schemes derived in equidistant Cartesian coordinate system. The conservative properties of finite difference schemes constructed in this research in generalized curvilinear system are examined by numerical tests of two dimensional inviscid flow with periodic domains. It is confirmed that the modified finite difference scheme in a colocated grid layout conserves the mass and kinetic energy properly even in nonorthogonal nonuniform computational grid. The conservative properties of the finite difference scheme in a staggered grid layout is also proper only when computational grids are orthogonal. In addition, direct numerical simulation of plane channel flows with fairly coarse mesh at Re(sub tau) = 180 are conducted using the finite difference schemes in generalized curvilinear coordinate system. It is found that the results are improved by the modified f, 複雑な流れ形状内の乱流の直接数値計算(DNS)または大規模渦シミュレーション(LES)を行うために、高精度な有限差分法が一般曲線座標系において必要である。最近、有限差分法を用いた非圧縮性乱流の数値計算において正確で安定した解を得るためには、一連の基礎方程式の解析的保存特性が、離散化基礎方程式においてさえ適切に満たされる必要のあることが示された。本報では、非圧縮性粘性流の座標変換基礎方程式の解析的保存特性は、正規直交座標におけるそれらと同一であることが示した。ここで扱う基礎方程式は、連続の式、ナビエ・ストークス方程式および速度2乗量と運動エネルギーの輸送方程式である。非圧縮性乱流の数値計算に適した一般曲線座標系における有限差分スキームは等間隔正規直交座標系で誘導された適切な有限差分スキームの比較的簡単な拡張で構成されている。本研究で構成した一般座標系有限差分スキームの保存特性を調査するために2次元周期的非粘性流の数値実験を行った。コロケート格子系修正有限差分スキームは、非直交不等間隔計算格子におてさえも質量および運動エネルギーを適切に保存することが確認できた。スタガード格子系有限差分スキームの保存特性もまた、計算格子が直交の場合、適切である。さらに、一般曲線座標系有限差分スキームを用いてレイノルズ数Re(sub τ)=180の平行平板間内乱流に対して非常に粗い格子点数での直接数値計算を行った。レギュラ格子系における連続の式の残差が減少するので、本結果が修正コロケート格子系差分スキームによって改善されることが判明した。

Published
2015

45. アクチュエータ・ディスク・モデルを用いた風車後流のラージ・エディ・シミュレーション: 風車タワーが風速分布に与える影響

Author

Kono, Takaaki and Kogaki, Tetsuya

Subjects
Physics::Fluid Dynamics, Actuator disk model, Large-eddy simulation, Astrophysics::High Energy Astrophysical Phenomena, Wind turbine wake, Physics::Space Physics, ラージ・エディ・シミュレーション, Astrophysics::Solar and Stellar Astrophysics, アクチュエータ・ディスク・モデル, 風車後流, Physics::Atmospheric and Oceanic Physics
Abstract

This study investigated the influence of a wind turbine tower on the wind velocity distribution in the wake of a wind turbine. Large-eddy simulation (LES) of the wind flow around the wind turbine was erformed using an actuator disk model for the rotor and by explicitly resolving the tower and nacelle. In addition, LES with no tower was performed. With regard to the streamwise component of the wind velocity in the wind turbine wake, the LES with tower reproduced the asymmetric distribution in thelateral direction, which was observed in a wind tunnel experiment, while the LES with no tower produced symmetric distribution. From the visualization of the LES results, it was considered that the enhanced turbulence and decreased velocity of wind flow behind the tower were attributable to the above-mentioned asymmetric wind velocity distribution predicted by the LES with tower.

Published
2012

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